Before his current role on Once Upon A Time, I couldn't see it, but, seeing what he's done with Rumplestiltskin, I could totally see him as a Doctor now (Not that I would expect anything Rumplestiltskin-like from his portrayal of the Doctor, but, the few roles of his I saw previously just didn't point to him being at all appropriate for The Doctor. Seeing him as Rumple in OUAT is a total departure from what I typically see of him)

^I haven't seen Rumplestiltskin, but I've imagined in the past that a Carlyle Doctor would be sort of a mix of Eccleston and Tennant. Though now that he's a bit older, maybe there'd be a dash of Troughton in there too.